The present invention generally relates to the field of intravascular medical devices, and more specifically to the field of guide catheters for placing balloon catheters and other similar diagnostic or therapeutic catheters within the body for treatment and diagnosis of diseases. In particular, the present invention relates to an improved guide catheter shaft design and corresponding methods of manufacture.
Several types of catheters are utilized for intravascular treatment. Examples of intravascular catheters include guide catheters, angioplasty catheters, stent delivery devices, angiographic catheters, neuro catheters, and the like.
Guide catheters are commonly used during coronary angioplasty procedures to aid in delivering a balloon catheter or other interventional medical devices to a treatment site in a vessel or other lumen within the body. In a routine coronary angioplasty procedure, a guiding catheter is introduced into a peripheral artery and advanced over a guidewire through the aorta until the distal end of the guide catheter is engaged with the appropriate coronary ostium. Next, a balloon dilatation catheter is introduced over the guidewire and through the guide catheter. The guidewire is advanced past the distal end of the guide catheter within the lumen of the diseased vessel and manipulated across the region of the stenosis. The balloon dilatation catheter is then advanced past the distal end of the guide catheter over the guidewire until the balloon is positioned across the treatment site. After the balloon is inflated to dilate the blood vessel in the region of the treatment site, the guidewire, balloon dilatation catheter and guide catheter can be withdrawn.
Guide catheters typically have preformed bends formed along their distal portion to facilitate placement of the distal end of the guide catheter into the ostium of a particular coronary artery of a patient. In order to function efficiently, guide catheters should have a relatively stiff main body portion and soft distal tip. The stiff main body portion gives the guide catheter sufficient xe2x80x9cpushabilityxe2x80x9d and xe2x80x9ctorqueabilityxe2x80x9d to allow the guide catheter to be inserted percutaneously into a peripheral artery, moved and rotated in the vasculature to position the distal end of the catheter at the desired site adjacent to a particular coronary artery. However, the distal portion should have sufficient flexibility so that it can track over a guidewire and be maneuvered through a tortuous path to the treatment site. In addition, a soft distal tip at the very distal end of the catheter should be used to minimize the risk of causing trauma to a blood vessel while the guide catheter is being moved through the vasculature to the proper position.
Angiographic catheters can be used in evaluating the progress of coronary artery disease in patients. Angiography procedures are used to view the patency of selected blood vessels. In carrying out this procedure, a diagnostic catheter having a desired distal end curvature configuration may be advanced over a guidewire through the vascular system of the patient until the distal end of the catheter is steered into the particular coronary artery to be examined.
For most intravascular catheters, it is desirable to have both a small outer diameter and a large inner lumen. Having a small outer diameter allows the catheter to be maneuvered more easily once inserted into the body and may allow the catheter to reach more distal sites. Having a large inner lumen allows larger medical appliances to be inserted through the catheter and/or allow a higher volume of fluids to be injected through the inner lumen.
To aid the advancement of additional medical appliances through the catheter, the inner lumen is generally comprised of a lubricious polymer. Polytetrafluoroethylene (PTFE) is a lubricious polymer commonly utilized to form inner lumens for medical devices. Because of the material composition of PTFE, manufacturing processes are generally more limiting and time consuming.
To minimize the outer diameter of the catheter, and maximize the inner diameter of the inner lubricious lumen, a relatively thin catheter wall is needed. Thin-walled catheters generally lack sufficient strength to be useful in many medical procedures. Specifically, thin-walled catheters generally lack structural characteristics that aid a physician in routing the catheter through a patient""s tortuous vasculature (i.e., pushability, torqueability, and kinkability, among others). One way to enhance the structural characteristics of such thin-walled catheters is to provide a reinforcing braid or coil in the catheter wall. The braided reinforcing layer can be braided over the lubricious layer, and the outer layer can be extruded over the reinforcing layer.
It is still often desired to modify portions of the catheter to further enhance the pushability, torqueability, and kinkability characteristics of the catheter. Because of the difficulty associated with extrusion of multiple polymers in different regions of a catheter""s length, modifications are generally made ad hoc. These modifications generally involve removing material from specific portions of the catheter shaft and filling the voids with material having different physical properties than the material that was removed. Depending upon the desired effect, the regions may be filled with either more flexible material or more rigid material. Ultimately, changing the physical characteristics of a particular section of the catheter imparts new properties to the entire catheter.
The present invention provides a catheter shaft for use in a guide or diagnostic catheter with improved characteristics for accessing desired treatment sites. In a first preferred embodiment, the catheter shaft includes a distal shaft portion having an outer layer which has been at least partially removed through an ablation process to form a contoured outer surface generally following the contour of a braided support member therein. Tubular inserts are placed over the contoured surface to form an outer distal layer having desired flexibility characteristics for particular applications.
The catheter shaft generally includes an inner tubular member having a proximal portion, a distal portion, and a lumen extending longitudinally therethrough. The inner tubular member in preferably manufactured from a perfluoroalkoxy (PFA). The PFA has been found to provide sufficient lubricity for passing additional medical instruments through the lumen formed within the PFA inner tubular member. Further, the PFA is melt-processable, unlike polytetrafluoroethylene which has been used in prior guide or diagnostic catheters as a lubricious inner tubular member.
A support member is disposed over a substantial portion of the inner tubular member and conforms thereto. The support member layer is preferably an interwoven braided member made up of filaments which have been braided to conform to the outer surface of the inner tubular member. The exterior surface of the support member layer is generally contoured resulting from the weaving of the filaments. Further, it is preferred that at least one of the filaments of the support member layer is tungsten. The tungsten filament or filaments provides additional radiopacity to the shaft. It has been found that a combination of stainless steel filaments with tungsten filaments is preferred, with the tungsten filaments comprising no more than half of the total number of filaments. Desired flexibility characteristics are achieved with this combination. In a preferred embodiment, the tungsten filaments comprise no more than four of the total number of filaments.
A first outer tubular member is disposed over a substantial portion of the support member layer and the inner tubular member and conforming thereto. The first outer tubular member has a proximal portion and a distal portion. The distal portion of the outer tubular member has an outside diameter less than the outside diameter of the proximal portion. The distal portion of the outer tubular member has an outside surface which generally follows or conforms to the contour of the support member layer. A second outer tubular member is disposed over at least a portion of the distal portion of the first outer tubular member with the inside surface of this layer following the contour of the underlying layer and support member. In preferred embodiments, the second outer tubular member includes several tubular inserts which abut one another longitudinally. Each of the tubular inserts is selected for its particular performance characteristics, such as flexibility, to selectively form portions of the catheter shaft with desired flexibility. In this way, the flexibility of the overall catheter may be made to increase distally and terminate in a flexible distal tip. The user of discrete outer tubular member inserts or segments is disclosed in commonly assigned co-pending U.S. application Ser. No. 09/313,672, filed on May 18, 1999, entitled GUIDE CATHETER HAVING SELECTED FLEXURAL MODULUS SEGMENTS, the disclosure of which is incorporated herein by reference.